Gel permeation chromatography in the study of the molecular weight distribution of the copolymer vinyl chloride–vinyl acetate

A sample of the commercial copolymer vinyl chloride–vinyl acetate was fractionated by the GPC method in the preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, GPC in the analytical scale, chemical analysis, and IR spectroscopy. They were compared with those obtained by precipitation fractionation. The M?_w and [η] values from the light scattering and viscometry of fractions of the commercial copolymer were employed for the calculation of the Mark-Houwink equation valid in THF at 25°C for a copolymer with vinyl acetate content of 10–13%. Universal calibration of the [η]·M type was confirmed experimentally for the above polymer. Effects which could change the correct interpretation of the GPC data were discussed in detail. Correct interpretation of the GPC data showed an agreement between the GPC, light scattering, and viscometric data within 6–7%.     

Compatibility of Poly(vinyl chloride–vinyl acetate)/Polyester-based Polyurethane Blends

The compatibility of poly(vinyl chloride–vinyl acetate) copolymer (P(VC-VA)) with thermoplastic polyurethane elastomers (TPU) was studied using Fourier transform infrared spectroscopy, optical microscopy and solubility parameters. The Gibbs free energy of mixing for the polymer–solvent system was calculated. The mechanical studies show that decrease in the P(VC-VA)/TPU ratio decreases the tensile strength. © 1997 SCI     

Gel permeation chromatography in the study of the molecular weight distribution of the copolymer vinyl chloride–vinyl acetate. II. Influence of copolymer chemical composition

A set of statistical vinyl chloride–vinyl acetate copolymers of various vinyl acetate content was prepared. The samples were fractionated by preparative gel permeation chromatography (GPC), and the fractions were characterized by analytical GPC, light scattering, and viscometry. The original samples were characterized also by osmometry and chemical analysis. The molecular parameters calculated from GPC analysis using the universal calibration were correlated with those of light scattering measurements and viscometry. It was found that in the range of chemical compositions and molecular weights studied, the chemical composition does not significantly influence the results of GPC analysis.     

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions. II. Mechanical properties

Concentrated solutions of acrylonitrile polymers exhibit reversible gelation. The rate of gelation at 25°C. was determined for various solutions of an acrylonitrile copolymer containing 7.7% vinyl acetate in mixtures of dimethylacetamide (solvent) and water (nonsolvent) by measuring the shear modulus of the forming gel as a function of time. The mechanical properties were also measured on a series of gels formed by cooling solutions to ?78°C. It was found that both the rate of gelation at 25°C. and the modulus of gels formed at ?78°C. increase very rapidly as either the solids level of the solution of the water content of the solvent is increased. The gelation rate data wree correlated with the gel melting points of the gels. The results are discussed and compared with the analogous but limited data available for other systems.     

Effect of polymerization conditions on the melt rheological properties of vinyl chloride–vinyl acetate copolymers

Mathematical models have been developed which predict the composition, molecular weight, and melt rheological properties for vinyl chloride/vinyl acetate copolymers of inherent viscosity range 0.4–0.7 dL/g and bound vinyl acetate levels of 3.8–17.4%. The effect of polymer long chain branching on the viscous/elastic moduli ratio is discussed as well as the comparison of Tinius–Olsen melt index measurements vs. mechanical spectrometer results. The reactivity ratio for vinyl chloride/vinyl acetate comonomer pairs was remeasured and found to be significantly different from literature values.     

Synthesis of vinyl phenyl acetate and an evaluation of vinyl chloride/vinyl phenyl acetate copolymers

The synthesis of vinyl phenyl acetate, by an ester interchange reaction between phenyl acetic acid and vinyl acetate and utilizing a catalyst, is described. Copolymerization with vinyl chloride, in a suspension system and using a peroxide catalyst, is described on a laboratory and pilot plant scale. Monomer/copolymer compositions, for an initial charge consisting of vinyl chloride/vinyl phenyl acetate (80/20 by weight) are presented over a range of conversions, as an indication of reactivity ratios. Discs, molded from unstabilized copolymers, show very good clarity and color stability, which improve with increased comonomer loading. Some retention of unpolymerized vinyl phenyl acetate monomer occurred, and some increase in softening points resulted following two reprecipitations from acetone into excess methanol. Compound from a 96/4 vinyl chloride/vinyl phenyl acetate copolymer has better color stability than does an equivalent vinyl chloride/vinylidene chloride copolymer compound. The enhanced color and heat stability of the copolymers is attributed to the aromatic character of the comonomer vinyl phenyl acetate.     

Physical properties of some vinyl tetrahydroabietate and vinyl maleopimarate acid anhydride copolymers

The stress–strain and torsional characteristics of some experimental copolymers of vinyl tetrahydroabietate and vinyl maleopimarate acid anhydride with vinyl chloride and vinyl acetate have been determined. Similar studies were also undertaken on peroxide-cured compositions of a vinyl chloride-vinyl tetrahydroabietate copolymer. Elastie moduli for the uncured copolymers range from 80,200 to 338,000 psi. Cured compositions of vinyl chloride–vinyl tetrahydroabietate copolymer exhibited both lower and higher moduli than that of the uncured copolymer. Some of the cured compositions appear to have an improved impact resistance over that of the uncured polymers.     

Graft polymerization of vinyl acetate onto starch. Saponification to starch–g–poly(vinyl alcohol)

Graft polymerizations of vinyl acetate onto granular corn starch were initiated by cobalt-60 irradiation of starch-monomer-water mixtures, and ungrafted poly(vinylacetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. However, over half of the polymer was present as ungrafted poly-(vinyl acetate) (grafting efficiency less than 50%), and the graft copolymer contained only 34% grafted synthetic polymer (34% add-on). Lower irradiation doses produced lower conversions of monomer to polymer and gave graft copolymers with lower % add-on. Addition of minor amounts of acrylamide, methyl acrylate, and methacrylic acid as comonomers produced only small increases in % add-on and grafting efficiency. However, grafting efficiency was increased to 70% when a monomer mixture containing about 10% methyl methacrylate was used. Grafting efficiency could be increased to over 90% if the graft polymerization of vinyl acetate-methyl methacrylate was carried out near 0°C, although conversion of monomers to polymer was low and grafted polymer contained 40-50% poly(methyl methacrylate). Selected graft copolymers were treated with methanolic sodium hydroxide to convert starch–g–poly(vinyl acetate) to starch–g–poly(vinyl alcohol). The molecular weight of the poly(vinyl alcohol) moiety was about 30,000. The solubility of starch–g–poly(vinyl alcohol) in hot water was less than 50%; however, solubility could be increased by substituting either acid-modified or hypochlorite-oxidized starch for unmodified starch in the graft polymerization reaction. Vinyl acetate was also graft polymerized onto acid-modified starch which had been dispersed and partially solubilized by heating in water. A total irradiation dose of either 1.0 or 0.5 Mrad gave starch–g–poly(vinyl acetate) with about 35% add-on, and a grafting efficiency of about 40% was obtained. A film cast from a starch–g–poly(vinyl alcohol) copolymer in which homopolymer was not removed exhibited a higher ultimate tensile strength than a comparable physical mixture of starch and poly(vinyl alcohol).     

Transesterification and crosslinking of poly(vinyl chloride‐co‐vinyl acetate) copolymers in the melt

A new method to obtain hydroxylated poly(vinyl chloride) (PVC‐OH) and its crosslinking in the melt are studied. Starting from a vinyl chloride‐co‐vinyl acetate copolymer, a transesterification reaction in the presence of an alcohol during the processing of plasticized polymer is investigated as a function of the processing temperature and alcohol nature (1‐butanol or 1‐octanol). Reaction evolution is followed by ¹H‐NMR and IR spectroscopies. The best results are obtained for 1‐octanol, and they show the absence of secondary reactions and the progressive appearance of OH groups in the polymer as acetate groups disappear. On the other hand, crosslinking of the thus‐obtained PVC‐OH with hexamethylene diisocyanate (HMDI) during the processing is also studied. The gel content and the mechanical properties at 140°C are studied as a function of three crosslinking variables: number of OH groups present in the polymer, concentration of HMDI added to the polymer, and time of crosslinking. The results show that by optimizing those parameters it is possible to obtain gel contents up to 100% and an increase of 600% in the Young's modulus and 1300% in the ultimate tensile strength with respect to the plasticized PVC. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 621–630, 1999     

Surface photocrosslinking of ethylene–vinyl acetate copolymer films

Surface photocrosslinking of ethylene–vinyl acetate (EVAc) copolymer films containing benzophenone (BP) was investigated for the purpose of replacing a poly(vinyl chloride) floor. The photogelatin in the EVAc films was effectively observed after UV radiation in the presence of oxygen. The crosslinking reaction was initiated from the surface of the irradiated film, which was mainly due to the dehydrogenation and generation of macroradicals of polymer by the light absorption of BP. The experiments of polyethylene–VAc with BP showed that the VAc‐rich amorphous part in the EVAc copolymer works as a crosslinking site. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1741–1745, 2000     

Molecular weight distribution in a poly(vinyl chloride–vinyl acetate) copolymer

The molecular weight distribution of a vinyl chloride–vinyl acetate copolymer has been studied by three methods: (a) solution fractionation; (b) osmometry and light scattering; (c) gel permeation chromatography. In (a), the fractions were precipitated from a tetrahydrofuran solution by water, then characterized. The data yielded models for the intrinsic viscosity and the molecular weight distribution, in terms of the copolymer molecular weight. In (b), the unfractionated copolymer was characterized by osmometry and light scattering, using in the latter case the two currently accepted theories for the determination of the true weight-average molecular weight. Conflicting data suggest caution in the use of these theories. In (c), the original fractions served to establish a calibration curve which yielded exceptionally low results when applied to the analysis of the unfractionated VC–VAc copolymer. Further investigations using proposed universal calibration theories bring to light serious discrepancies.     

The rheological properties of vinyl chloride–vinyl acetate copolymers

Copolymers of vinyl chloride–vinyl acetate have been prepared with different vinyl acetate contents and molecular weights and under different polymerization conditions. A rheological study of these copolymers indicates that they behave in some ways like externally plasticized PVC. For instance, as the vinyl acetate content increases, the melt viscosity decreases, the flow activation energy decreases, and the copolymer becomes more Newtonian. However, the critical shear rate for melt fracture increases, resembling the addition of elastic polymers to PVC. An increase in copolymer molecular weight has a similar effect on the rheological behavior as in PVC, except that the flow activation energy is observed to increase rather than decrease. Decreasing the polymerization temperature affects the flow properties of the copolymer, probably due to changes in degree of branching and crystallinity. A copolymer made by the delayed addition of vinyl chloride, having a more random structure than one made by the conventional batch method, exhibited quite different flow behavior. It had a lower melt viscosity, higher critical shear rate, and lower flow activation energy.     

Synthesis and characterization of poly(vinyl chloride‐co‐vinyl acetate)‐graft‐poly[(meth)acrylates] by atom transfer radical polymerization

The graft polymerization of methyl methacrylate and butyl acrylate onto poly(vinyl chloride‐co‐vinyl acetate) with atom transfer radical polymerization (ATRP) was successfully carried out with copper(I) thiocyanate/N,N,N′,N′,N″‐pentamethyldiethylenetriamine and copper(I) chloride/2,2′‐bipyridine as catalysts in the solvent N,N‐dimethylformamide. For methyl methacrylate, a kinetic plot of ln([M]₀/[M]) (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration) versus time for the graft polymerization was almost linear, and the molecular weight of the graft copolymer increased with increasing conversion, this being typical for ATRP. The formation of the graft polymer was confirmed with gel permeation chromatography, ¹H‐NMR, and Fourier transform infrared spectroscopy. The glass‐transition temperature of the copolymer increased with the concentration of methyl methacrylate. The graft copolymer was hydrolyzed, and its swelling capacity was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 183–189, 2005     

Grafting of vinyl acetate onto poly(vinyl chloride) in solution

Radiation-induced grafting of vinyl acetate (VAc) onto poly(vinyl chloride) (PVC) was performed in solution with dimethylformamide (DMF). Grafting was studied as a function of dose, dose rate, and VAc/PVC ratio. The amount of grafting was measured by IR spectroscopy on the graft copolymer fraction insoluble in hot methanol. The homopolymerization of VAc was also studied in the same conditions, in order to check the influence of the solvent on radiochemical reactions leading to graft copolymers. The results show that the grafting can be easily obtained and the graft copolymer will be tested for the preparation of ultrafiltration membranes.     

Characterization of grafting in the emulsion polymerization of vinyl acetate using poly(vinyl alcohol) as stabilizer

Emulsion polymerizations of vinyl acetate (VAc) with polyvinyl alcohol (PVA) as emulsifier were carried out by both batch and semicontinuous processes. The extent of grafting of vinyl acetate onto the PVA chains was investigated by a new method for separating the various polymer fractions in high solids content latexes. The quantification was carried out by a three‐step separation and selective solubilization of the PVAc latexes. After the separation, the water‐soluble PVA and the solvent‐soluble PVAc components were characterized by gel permeation chromatography and ¹³C–NMR, from which the accuracy of this method was verified. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1739–1747, 2001     

Polyblends of poly(vinyl chloride) with ethylene/vinyl acetate copolymers: Practical properties and morphology

Five to 15 percent of ethylene/vinyl acetate copolymers was compounded into rigid polyvinyl chloride, with the copolymers dispersed as discrete micro-domains, produced very efficient synergistic improvement of impact strength; as the vinyl acetate content of the copolymer increased from 28 to 60 percent, the synergistic peak moved to higher copolymer content and became higher and broader. Copolymer content correlated directly with melt flow and thermal stability, and inversely to modulus, strength, and heat-deflection temperature. The vinyl acetate content of the copolymer correlated directly with elongation, impact strength, and thermal stability, but inversely to modulus, heat-deflection temperature, low-temperature flexibility, and melt flow. When the copolymer content reached 25 percent, it formed a second continuous-phase, interpenetrating the polymer network structure and acting as a polymeric plasticizer, producing thermoplastic elastoplastics.     

氯乙烯/丙烯酸酯二元及多元共聚物的研究进展

介绍了氯乙烯/丙烯酸酯多元共聚物、聚氯乙烯树脂/丙烯酸酯/顺丁烯二酰亚胺接枝共聚物、聚氯乙烯树脂/N-取代马来酸胺/丙烯酸酯接枝共聚树脂、氯乙烯/乙酸乙烯/丙烯酸羟丙酯共聚物、氯乙烯/乙酸乙烯/丙烯酸丁酯共聚乳液、聚丙烯酸酯-氯乙烯接枝共聚物、氯乙烯/乙烯/丙烯酸羟乙酯共聚涂料树脂、氯乙烯/丙烯酸甲酯共聚乳液的特点、生产工艺及其性能和用途.     

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions

The reversible gelation of acrylonitrile–vinyl acetate copolymers in concentrated solutions has been studied with the use of various solvents. These concentrated solutions gel or become rigid with time, but they become fluid again when heated above a certain temperature called the gel melting point. A technique involving the use of mercury drops was developed to measure this transition. This temperature was evaluated as a function of solids level, water content in the solvent, and the amount of vinyl acetate in the copolymer, dimethylacetamide being used as the solvent. Four other solvents were used to obtain limited data. Gel melting was studied further by differential thermal analysis and shear modulus measurements. The results are discussed in terms of network formation and solubility. The x-ray diffraction results imply that the tie points of the gel are crystalline.     

Study of dynamic mechanical properties of poly(vinyl chloride)–ethylene vinyl acetate copolymer and poly(vinyl chloride)–chlorinated ethylene vinyl acetate copolymer mixtures

The compatibility of the mixtures poly(vinyl chloride)—ethylene vinyl acetate copolymer and poly(vinyl chloride)—chlorinated ethylene vinyl acetate copolymer was studied by the method of dynamic mechanical testing. The character of G′ and G″ was confronted with the Takayanagi model. In all cases a limited compatibility of the components was observed.     

Miniemulsion and macroemulsion copolymerization of vinyl acetate with vinyl versatate

The miniemulsion and macroemulsion polymerization of vinyl acetate with vinyl versatate in batch and semibatch systems was investigated. Vinyl versatate was added either as an emulsion with the vinyl acetate, or as a neat liquid stream. In the batch runs, there is a poor dispersion of vinyl versatate during the nucleation period for the runs in which the vinyl versatate was added neat at the beginning of the polymerization. This led to smaller particles, lower polymerization rate, and different polymer composition evolution when compared with runs in which the vinyl versatate was emulsified with the vinyl acetate. In seeded semibatch runs, residual surfactant in the seed latex, along with the propensity for homogeneous nucleation in vinyl acetate emulsions, resulted in continuing nucleation during the entire semibatch interval. The polymerization rate was primarily affected by monomer feed rate rather than the feeding mode. The effect of monomer feeding mode on copolymer composition was weak when the semibatch feed rate was low, indicating some level of vinyl versatate mass transfer resistance. In all runs, only one glass transition temperature was observed, indicating effective copolymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2219–2229, 2002